It is predicted that approximately 4,000,000 people will be diagnosed with nonmelanoma skin cancer this year in the United States. Seventy-five percent of these patients will undergo traditional excisional surgery, i.e. non- Mohs Micrographic Surgery (non-MMS). Unlike MMS surgery traditional excision surgeries do not employ methods to determine the status of the margins of resected tissues during the surgical procedure. Instead the size of margins to be resected is determined by the size and differentiation of the lesion observed during pre- surgical examination and diagnosis. Resected specimens are forwarded to pathology where they undergo formalin fixation, paraffin embedding, staining, and analysis, with results available 1- days post-surgery. In general these are larger lesions so only a limited portion (approximately 1%) of the margin is analyzed by pathologists to deduce if the surgery removed all of the cancer. Normally, to ensure total removal of the cancer and prevent re-excision, more aggressive margins, up to 1 mm, may be taken with non-MMS than with MMS surgery. With MMS less aggressive margins are taken but are immediately subjected to iterative frozen section analysis (with 100% of the margins analyzed) during the surgical procedure. MMS achieves up to 99% cure rates and significantly limits the morbidity compared to non-Mohs procedures. However, MMS is not available at all dermatology facilities nor is it considered appropriate use for approximately 7 % of non-melanoma skin cancers. Therefore the majority of skin cancers undergo conventional surgery followed by pathological analysis to determine if all the cancer was removed. However, non-MMS procedures do not has the same cure rates as MMS and substantial numbers of patients are forced to return for re-excision of cancer missed during the initial skin cancer excision. Therefore, there exists an unmet clinical need to assess surgical margins during non-MMS procedures, reducing the number of re- excisions and potentially impacting patient outcomes. Development of a simple, rapid, and global imaging technology to rapidly and intra-operatively identify cancer in resected tissues during surgery could bring MMS- like results to non-MMS skin cancer resections. In our a technology a quenched protease-selective optical imaging probe is used to identify skin cancer (both basal cell and squamous cell carcinomas) after a topical application of the probe to excised skin cancer tissues. Our technology achieves 99% sensitivity and 90% specificity. In this proposal we have brought together two partners, INDEC Systems Inc. (camera technology) and Case Western Reserve University (assessment of instrument performance, coordination with UH clinicians) to drive to the clinic a product capable of impacting the way skin cancers are resected. We propose the development and testing of a complete solution to assess excised skin cancer margins. Our complete approach topically applies a quenched protease selective imaging probe to excised tissues and then images these tissues in a dedicated imaging device to identify the location of both cancer and normal skin.